For crab cakes, in medium mixing bowl, combine butter, onion, carrot, green pepper and parsley.
Cover.
Microwave at High for 2 to 3 minutes, or until vegetables are tender, stirring once.
Add remaining crab cake ingredients, except cornflake crumbs.
Mix well.
Shape into 4 patties, about 1 inch thick.
Dip both sides of each patty in cornflake crumbs, pressing lightly to coat.
Arrange on roasting rack.
Set aside.
For sauce, place butter in 4-cup measure.
Microwave at High for 45 seconds to 1 minute, or until butter melts.
Stir in flour, salt, cayenne and mustard.
Blend in milk.
Microwave at High for 3 to 4 minutes, or until mixture thickens and bubbles, stirring after every minute.
Stir in cheese until melted.
Cover.
Set aside.
For crab cakes, microwave at 70% (Medium High) for 5 to 9 minutes, or until firm, rotating rack after every 3 minutes.